Image projection devices that utilize a light bulb to illuminate a slide transparency or film in combination with a lens to enlarge the image onto a viewing surface are well known. Slide projectors for viewing 35 mm slides came into widespread use during the 1950s for home entertainment and educational uses. These slide projectors included an electric incandescent light bulb or other light source, a condensing lens or reflector to direct light onto the slide, a slide holder, and a focusing lens. Slide projectors have fallen out of use in favor of more convenient digital media shown on a projection screen using a video projector or displayed on a large video monitor.
Flashlight projectors are a novelty or toy item that use a flashlight as the light source to illuminate a slide transparency. These devices typically include a mechanism to attach to the flashlight, a mechanism to mount the slide in position, and optics to focus and enlarge the slide image. Examples include U.S. Pat. Nos. 2,445,651, 2,478,336, and 5,321,449.
Mobile devices, such as smart phones, digital cameras and tablet computing devices, can also be equipped with an image projector. This type of technology typically uses a liquid crystal on silicon display with an LED to illuminate the display. Adding an image projector to a mobile device can significantly increase the costs of producing the mobile device.